I think it's worth adding: the domains that these organisations rank are chosen by those organisations. How the ranking works is chosen by the ranking org. A major source of revenue for the ranking orgs is conference sponsorships, and one of the things included in those sponsorships is access to the analysts writing the reports.
It's also worth noting that ranking companies don't rank products, they rank vendors. So a company that does everything kind of ok over multiple products can get an advantage over a company that solves one problem very well with one product, if the ranking companies choose to define the category in an overly broad way.
It's also worth noting that ranking companies don't rank products, they rank vendors. So a company that does everything kind of ok over multiple products can get an advantage over a company that solves one problem very well with one product, if the ranking companies choose to define the category in an overly broad way.